版权声明： https://blog.csdn.net/qccz123456/article/details/81908079
使用libpmemblk能直接访问storage（DAX），支持 load/store access，不需要 paging blocks。
libpmemblk API说明：http://pmem.io/pmdk/manpages/linux/master/libpmemblk/libpmemblk.7.html
Key：
pmemblk_create() // 创建pmem的内存块
pmemblk_open() // 打开已创建的内存块
pmemblk_nblock() // 获得某内存块内分片元素数量
pmemblk_write() // 将数据写入某分片元素
pmemblk_read() // 从某分片元素中读出数据
pmemblk_set_zero() // 将某分片元素设置成0
pmemblk_close() // 关闭内存块
pmemblk_set_funcs() // 允许用户覆盖libpmemblk内的malloc、free等函数，实现自定义malloc、free等
例子：
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <libpmemblk.h>
#define POOL_SIZE ((size_t)(1024 * 1024 * 1024)) /* size of the pmemblk pool -- 1 GB */
#define ELEMENT_SIZE 1024 /* size of each element in the pmem pool */
int main(int argc, char *argv[])
{
const char path[] = "/root/hostnme/pmemblk.002";
char buf[ELEMENT_SIZE];
char rcv[ELEMENT_SIZE];
/* create the pmemblk pool or open it if it already exists */
PMEMblkpool *pbp = pmemblk_create(path, ELEMENT_SIZE, POOL_SIZE, 0666);
if (pbp == NULL)
pbp = pmemblk_open(path, ELEMENT_SIZE);
if (pbp == NULL) {
perror(path);
exit(1);
}
/* how many elements fit into the file? */
size_t nelements = pmemblk_nblock(pbp);
printf("file holds %zu elements\n", nelements);
/* store a block at index 5 */
strcpy(buf, "hello, world");
printf("buf: %s\n", buf);
if (pmemblk_write(pbp, buf, 0) < 0 ||
pmemblk_write(pbp, buf, 5) < 0 ||
pmemblk_write(pbp, buf, 6) < 0) {
perror("pmemblk_write");
exit(1);
}
/* read the block at index 5 */
if (pmemblk_read(pbp, rcv, 5) < 0) {
perror("pmemblk_read");
exit(1);
}
printf("rcv: %s\n", rcv);
/* read the block at index 10 (reads as zeros initially) */
if (pmemblk_read(pbp, rcv, 10) < 0) {
perror("pmemblk_read");
exit(1);
}
printf("rcv: %s\n", rcv);
/* zero out the block at index 5 */
if (pmemblk_set_zero(pbp, 5) < 0) {
perror("pmemblk_set_zero");
exit(1);
}
/* read the block at index 5 */
if (pmemblk_read(pbp, rcv, 5) < 0) {
perror("pmemblk_read");
exit(1);
}
printf("rcv: %s\n", rcv);
pmemblk_close(pbp);
return 0;运行结果如下：POOL_SIZE 除以 ELEMENT_SIZE 为 1024*1024，但结果为1044204，说明pmemblk创建时占用了部分字节，需根据pmemblk_nblock()得到pmemblk_create()创建得到的实际block数量。
$ ./manpage
file holds 1044204 elements
buf: hello, world
rcv: hello, world
rcv:
rcv:通过pmempool查看结果，每一个block（0x000037f0减0x00003400等于1009），说明实际每个block中并没有1024的element，注意一下hello, world总共12个字符（中间有空格）对应与前面的12个字节68 65 6c 6c 6f 2c 20 77 6f 72 6c 64，中间无分隔符：
$ ./pmempool info -d /root/hostname/pmemblk.002 --skip-zeros
Part file:
path : /root/hostname/pmemblk.002
type : regular file
size : 1073741824
POOL Header:
Signature : PMEMBLK
Major : 1
Mandatory features : 0x0
Not mandatory features : 0x0
Forced RO : 0x0
Pool set UUID : 6aa96390-7748-4991-bccf-9c535261f909
UUID : c5af766e-054f-4b09-93ee-44efd89a0c40
Previous part UUID : c5af766e-054f-4b09-93ee-44efd89a0c40
Next part UUID : c5af766e-054f-4b09-93ee-44efd89a0c40
Previous replica UUID : c5af766e-054f-4b09-93ee-44efd89a0c40
Next replica UUID : c5af766e-054f-4b09-93ee-44efd89a0c40
Creation Time : Wed Aug 22 2018 21:31:40
Alignment Descriptor : 0x000007f737777310[OK]
Class : 64
Data : 2's complement, little endian
Machine : AMD X86-64
Last shutdown : clean
Checksum : 0xdc5e837e32c6a106 [OK]
PMEM BLK Header:
Block size : 1024
Is zeroed : true
[ARENA 0]
PMEM BLK BTT Info Header:
Signature : BTT_ARENA_INFO
UUID of container : 6aa96390-7748-4991-bccf-9c535261f909
Flags : 0x0
Major : 1
Minor : 1
External LBA size : 1024
External LBA count : 1044204
Internal LBA size : 1024
Internal LBA count : 1044460
Free blocks : 256
Info block size : 4096
Next arena offset : 0x0
Arena data offset : 0x1000
Area map offset : 0x3fbfd000
Area flog offset : 0x3fff9000
Info block backup offset : 0x3fffd000
Checksum : 0x39e2a520dc291ae3 [OK]
PMEM BLK blocks data:
Block 0: offset: 0x00000001 state: normal
00003400 68 65 6c 6c 6f 2c 20 77 6f 72 6c 64 00 00 00 00 |hello, world....|
00003410 00 00 00 00 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |..........#.,...|
*
00003430 04 00 00 00 00 00 00 00 28 4d 7b 09 2c 7f 00 00 |........(M{.,...|
00003440 04 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00003450 0d 39 8a 92 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |.9........#.,...|
00003460 e1 e5 49 92 02 80 ff ff 28 4d 7b 09 2c 7f 00 00 |..I.....(M{.,...|
00003470 04 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00003480 57 db 93 1c 00 00 00 00 fb 9c 23 0a 2c 7f 00 00 |W.........#.,...|
00003490 b1 e5 49 92 02 80 ff ff 10 1a b6 6d fd 7f 00 00 |..I........m....|
000034a0 d0 37 7b 09 2c 7f 00 00 68 9d 7b 09 2c 7f 00 00 |.7{.,...h.{.,...|
000034b0 20 1b b6 6d fd 7f 00 00 10 1b b6 6d fd 7f 00 00 | ..m.......m....|
000034c0 17 00 00 00 00 00 00 00 15 cf 89 09 2c 7f 00 00 |............,...|
000034d0 00 00 00 00 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |..........#.,...|
000034e0 18 fa 44 0a 2c 7f 00 00 00 4f b7 09 2c 7f 00 00 |..D.,....O..,...|
000034f0 03 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00003500 31 6e d5 35 00 00 00 00 fb 9c 23 0a 2c 7f 00 00 |1n.5......#.,...|
00003510 30 57 65 01 00 00 00 00 90 1a b6 6d fd 7f 00 00 |0We........m....|
00003520 ec 4c b7 09 2c 7f 00 00 d8 61 b7 09 2c 7f 00 00 |.L..,....a..,...|
00003530 a0 1b b6 6d fd 7f 00 00 90 1b b6 6d fd 7f 00 00 |...m.......m....|
00003540 31 00 00 00 2c 7f 00 00 c0 1a b6 6d fd 7f 00 00 |1...,......m....|
00003550 00 00 00 00 00 00 00 00 30 59 43 0a 2c 7f 00 00 |........0YC.,...|
00003560 50 f5 44 0a 2c 7f 00 00 55 a9 ff 09 2c 7f 00 00 |P.D.,...U...,...|
00003570 50 6e b7 09 2c 7f 00 00 98 95 ff 09 2c 7f 00 00 |Pn..,.......,...|
00003580 00 00 00 00 01 00 00 00 c9 00 00 00 01 00 00 00 |................|
00003590 18 fa 44 0a 2c 7f 00 00 58 1c b6 6d fd 7f 00 00 |..D.,...X..m....|
000035a0 30 1c b6 6d fd 7f 00 00 01 00 00 00 00 00 00 00 |0..m............|
000035b0 30 59 43 0a 2c 7f 00 00 20 0a 45 0a 2c 7f 00 00 |0YC.,... .E.,...|
000035c0 c8 06 45 0a 2c 7f 00 00 df 9f 23 0a 2c 7f 00 00 |..E.,.....#.,...|
000035d0 00 00 00 00 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |..........#.,...|
000035e0 01 00 00 00 2c 7f 00 00 28 4d 7b 09 2c 7f 00 00 |....,...(M{.,...|
000035f0 04 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00003600 2e 4e 3d f6 00 00 00 00 fb 9c 23 0a 2c 7f 00 00 |.N=.......#.,...|
00003610 01 00 00 00 2c 7f 00 00 90 1b b6 6d fd 7f 00 00 |....,......m....|
00003620 30 4b 7b 09 2c 7f 00 00 a8 11 7c 09 2c 7f 00 00 |0K{.,.....|.,...|
00003630 a0 1c b6 6d fd 7f 00 00 90 1c b6 6d fd 7f 00 00 |...m.......m....|
00003640 2e 00 00 00 00 00 00 00 55 a9 ff 09 2c 7f 00 00 |........U...,...|
00003650 00 00 00 00 00 00 00 00 40 58 43 0a 2c 7f 00 00 |........@XC.,...|
00003660 18 fa 44 0a 2c 7f 00 00 d1 05 40 00 00 00 00 00 |..D.,.....@.....|
00003670 78 1d 7c 09 2c 7f 00 00 60 03 40 00 00 00 00 00 |x.|.,...`.@.....|
00003680 00 00 00 00 01 00 00 00 30 08 00 00 01 00 00 00 |........0.......|
00003690 d0 19 7c 09 2c 7f 00 00 58 1d b6 6d fd 7f 00 00 |..|.,...X..m....|
000036a0 30 1d b6 6d fd 7f 00 00 01 00 00 00 00 00 00 00 |0..m............|
000036b0 40 58 43 0a 2c 7f 00 00 a8 34 45 0a 2c 7f 00 00 |@XC.,....4E.,...|
000036c0 50 31 45 0a 2c 7f 00 00 df 9f 23 0a 2c 7f 00 00 |P1E.,.....#.,...|
000036d0 00 00 00 00 00 00 00 00 40 58 43 0a 2c 7f 00 00 |........@XC.,...|
000036e0 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000036f0 01 00 00 00 fd 7f 00 00 50 31 45 0a 2c 7f 00 00 |........P1E.,...|
00003700 01 00 00 00 fd 7f 00 00 00 00 00 00 00 00 00 00 |................|
00003710 01 00 00 00 00 00 00 00 d8 61 b7 09 2c 7f 00 00 |.........a..,...|
00003720 00 00 00 00 00 00 00 00 a8 34 45 0a 2c 7f 00 00 |.........4E.,...|
00003730 a0 1c b6 6d fd 7f 00 00 90 1c b6 6d fd 7f 00 00 |...m.......m....|
00003740 2e 4e 3d f6 00 00 00 00 d1 05 40 00 00 00 00 00 |.N=.......@.....|
00003750 ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00003760 a8 11 7c 09 2c 7f 00 00 18 fa 44 0a 2c 7f 00 00 |..|.,.....D.,...|
00003770 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00003780 72 65 67 69 6f 6e 00 53 74 61 72 74 20 74 72 61 |region.Start tra|
00003790 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
000037b0 72 65 67 69 6f 6e 00 53 74 61 72 74 20 74 72 61 |region.Start tra|
000037c0 00 00 00 00 00 00 00 00 38 20 60 00 00 00 00 00 |........8 `.....|
000037d0 c0 08 40 00 00 00 00 00 90 1e b6 6d fd 7f 00 00 |[email protected]....|
000037e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
000037f0 00 00 00 00 00 00 00 00 1e e9 23 0a 2c 7f 00 00 |..........#.,...|
------------------------------------------------------------------------------
Block 6: offset: 0x00000006 state: normal
00004800 68 65 6c 6c 6f 2c 20 77 6f 72 6c 64 00 00 00 00 |hello, world....|
00004810 00 00 00 00 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |..........#.,...|
*
00004830 04 00 00 00 00 00 00 00 28 4d 7b 09 2c 7f 00 00 |........(M{.,...|
00004840 04 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00004850 0d 39 8a 92 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |.9........#.,...|
00004860 e1 e5 49 92 02 80 ff ff 28 4d 7b 09 2c 7f 00 00 |..I.....(M{.,...|
00004870 04 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00004880 57 db 93 1c 00 00 00 00 fb 9c 23 0a 2c 7f 00 00 |W.........#.,...|
00004890 b1 e5 49 92 02 80 ff ff 10 1a b6 6d fd 7f 00 00 |..I........m....|
000048a0 d0 37 7b 09 2c 7f 00 00 68 9d 7b 09 2c 7f 00 00 |.7{.,...h.{.,...|
000048b0 20 1b b6 6d fd 7f 00 00 10 1b b6 6d fd 7f 00 00 | ..m.......m....|
000048c0 17 00 00 00 00 00 00 00 15 cf 89 09 2c 7f 00 00 |............,...|
000048d0 00 00 00 00 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |..........#.,...|
000048e0 18 fa 44 0a 2c 7f 00 00 00 4f b7 09 2c 7f 00 00 |..D.,....O..,...|
000048f0 03 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00004900 31 6e d5 35 00 00 00 00 fb 9c 23 0a 2c 7f 00 00 |1n.5......#.,...|
00004910 30 57 65 01 00 00 00 00 90 1a b6 6d fd 7f 00 00 |0We........m....|
00004920 ec 4c b7 09 2c 7f 00 00 d8 61 b7 09 2c 7f 00 00 |.L..,....a..,...|
00004930 a0 1b b6 6d fd 7f 00 00 90 1b b6 6d fd 7f 00 00 |...m.......m....|
00004940 31 00 00 00 2c 7f 00 00 c0 1a b6 6d fd 7f 00 00 |1...,......m....|
00004950 00 00 00 00 00 00 00 00 30 59 43 0a 2c 7f 00 00 |........0YC.,...|
00004960 50 f5 44 0a 2c 7f 00 00 55 a9 ff 09 2c 7f 00 00 |P.D.,...U...,...|
00004970 50 6e b7 09 2c 7f 00 00 98 95 ff 09 2c 7f 00 00 |Pn..,.......,...|
00004980 00 00 00 00 01 00 00 00 c9 00 00 00 01 00 00 00 |................|
00004990 18 fa 44 0a 2c 7f 00 00 58 1c b6 6d fd 7f 00 00 |..D.,...X..m....|
000049a0 30 1c b6 6d fd 7f 00 00 01 00 00 00 00 00 00 00 |0..m............|
000049b0 30 59 43 0a 2c 7f 00 00 20 0a 45 0a 2c 7f 00 00 |0YC.,... .E.,...|
000049c0 c8 06 45 0a 2c 7f 00 00 df 9f 23 0a 2c 7f 00 00 |..E.,.....#.,...|
000049d0 00 00 00 00 00 00 00 00 c4 95 23 0a 2c 7f 00 00 |..........#.,...|
000049e0 01 00 00 00 2c 7f 00 00 28 4d 7b 09 2c 7f 00 00 |....,...(M{.,...|
000049f0 04 00 00 00 00 00 00 00 16 00 00 00 00 00 00 00 |................|
00004a00 2e 4e 3d f6 00 00 00 00 fb 9c 23 0a 2c 7f 00 00 |.N=.......#.,...|
00004a10 01 00 00 00 2c 7f 00 00 90 1b b6 6d fd 7f 00 00 |....,......m....|
00004a20 30 4b 7b 09 2c 7f 00 00 a8 11 7c 09 2c 7f 00 00 |0K{.,.....|.,...|
00004a30 a0 1c b6 6d fd 7f 00 00 90 1c b6 6d fd 7f 00 00 |...m.......m....|
00004a40 2e 00 00 00 00 00 00 00 55 a9 ff 09 2c 7f 00 00 |........U...,...|
00004a50 00 00 00 00 00 00 00 00 40 58 43 0a 2c 7f 00 00 |........@XC.,...|
00004a60 18 fa 44 0a 2c 7f 00 00 d1 05 40 00 00 00 00 00 |..D.,.....@.....|
00004a70 78 1d 7c 09 2c 7f 00 00 60 03 40 00 00 00 00 00 |x.|.,...`.@.....|
00004a80 00 00 00 00 01 00 00 00 30 08 00 00 01 00 00 00 |........0.......|
00004a90 d0 19 7c 09 2c 7f 00 00 58 1d b6 6d fd 7f 00 00 |..|.,...X..m....|
00004aa0 30 1d b6 6d fd 7f 00 00 01 00 00 00 00 00 00 00 |0..m............|
00004ab0 40 58 43 0a 2c 7f 00 00 a8 34 45 0a 2c 7f 00 00 |@XC.,....4E.,...|
00004ac0 50 31 45 0a 2c 7f 00 00 df 9f 23 0a 2c 7f 00 00 |P1E.,.....#.,...|
00004ad0 00 00 00 00 00 00 00 00 40 58 43 0a 2c 7f 00 00 |........@XC.,...|
00004ae0 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00004af0 01 00 00 00 fd 7f 00 00 50 31 45 0a 2c 7f 00 00 |........P1E.,...|
00004b00 01 00 00 00 fd 7f 00 00 00 00 00 00 00 00 00 00 |................|
00004b10 01 00 00 00 00 00 00 00 d8 61 b7 09 2c 7f 00 00 |.........a..,...|
00004b20 00 00 00 00 00 00 00 00 a8 34 45 0a 2c 7f 00 00 |.........4E.,...|
00004b30 a0 1c b6 6d fd 7f 00 00 90 1c b6 6d fd 7f 00 00 |...m.......m....|
00004b40 2e 4e 3d f6 00 00 00 00 d1 05 40 00 00 00 00 00 |.N=.......@.....|
00004b50 ff ff ff ff 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00004b60 a8 11 7c 09 2c 7f 00 00 18 fa 44 0a 2c 7f 00 00 |..|.,.....D.,...|
00004b70 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00004b80 72 65 67 69 6f 6e 00 53 74 61 72 74 20 74 72 61 |region.Start tra|
00004b90 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00004bb0 72 65 67 69 6f 6e 00 53 74 61 72 74 20 74 72 61 |region.Start tra|
00004bc0 00 00 00 00 00 00 00 00 38 20 60 00 00 00 00 00 |........8 `.....|
00004bd0 c0 08 40 00 00 00 00 00 90 1e b6 6d fd 7f 00 00 |[email protected]....|
00004be0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00004bf0 00 00 00 00 00 00 00 00 1e e9 23 0a 2c 7f 00 00 |..........#.,...|
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